I am not sure a foil would generate 90 kgs of lift for that little drag. Can anyone concur that statement as I'm a dummy with maths

At 0.05 m>2 this would mean a practical foil with a modern section and aspect ratio of about 1.25 metres long x 75mm wide. Now the loading would be so high at the tips that a huge amount of carbon would be needed such that I would doubt that you could construct such a wide beastie. OK reduce the width to say 75cms which is still a really wide wing on a rudder, down comes the aspect ratio, up goes the drag, add in a few dings etc and surface impections and up goes the drag even further, mmmmmm not looking so good now.

For all those maths boys, how much force in regards to foward motion does a F16 Spinnaker actually produce, I bet its not that many kilos as one can fairly easily hold on the sheet which is taking probably more than a third of the load. Interesting calculation

Yes Glen on my Stealth when the windward T foil comes out of the water the leeward bow immediately buries, fortunately the Stealths have ample reserve in the bows and generally the boat wants to submarine along its length to such an extent that the drag slows the boat and the sheet loads go so high that one tends to dump the sheet rather than pitchpole.

Still not convinced that in a practical sense adjustiable foils are any worry, if in doubt simply put an upper limit on the foil sq mtr size.